Sanding machine



Oct. 6, 1931. l|=. H. JOHNSON- SANDING uAcHIN Filed uay-14, 1927 Patented oa. s, 1931 UNiTED -'s'lza'rEs FREDERICK E. JOHNSON,

PATENT OFFICE 'on DETROIT, MICHIGAN summe MACHINE y `App1ieation led May 14,

vide a housing adapted to be manually supported having a pair of relatively adjustable primary windings carried thereby adapted to produce a rotatving magnetic field which solely ei'ects` rotation of belt pulleys supported by the housing.

Other objects and advantages will more fully appear from the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is a side elevation of my improved device, with the belt backing shoe shown in Y is secured the rear handle 12.

section.

Fig. 2 is a plan view of Fig. 1, parts being broken away and parts shown in section.

Fig. 3 is a sectional view thrir the stationary primary windings and the rotatable pulley; and

Fig. 4 is a side view of the adjustable support for one of the pulleys.

Referring to the drawings, wherein a preferred form of my invention has been illustrated, a housing 10 is shown provided with a rear handle 12 and a forward handle 14 extending at right angles to the rear handle 12. Suitable electrical conductors 16, adapted to be connected to any convenient' source of electrical energy, are'extended thru the forward handle 14 across the top of the housing 1Q into a raised portion 18 to which A cover 20, detachably secured to the portion 18, covers the conductors 16 leading to a switch 22 in the rear handle 12.

`The housing 10 comprises a top portion 1927. Serial No. 192,473.

24 and a side portion 26. The side portion 26 is provided with a split boss 28 which receives a support 30 for one of the'pulleys and a boss 32 which receives an adjustable support 34 for the other pulley. The sup- 55 port 30 is provided with a portion 36'which 1s received in the split boss 28 and clamped therein-by a screw 38 engaging flanges 40 of the boss to pinch it around the portion 36.

A flange'42 is adapted to form an end plate 60 for the mechanism carried by the support and engages the side portion 26 vto position the support axially. A belt pulley 44 is secured to a shaft 46 rotatably supported in an inner boss 48 of the support 30. A sleeve 55 50, xed to the boss 48, surrounds the shaft 46 and has its outer periphery provided with a plurality of steel plates 52 with windings 54 around portions thereof, to form a plurality of poles 56, constituting the primary 7 or stator of an induction motor. A bearing 58 is mounted in the inner periphery of the sleeve 50 to take the radial load of the shaft and pulley. Mounted on the inner periphery of the pulley 44 are a plurality of steel 75 plates 60 held together by rivets 62 or any means adapted to form' therebetween poles 64 which constitute the secondary or rotor of an inductionmotor. The rotor is provided with fins 66 which act as fan blades to cause 8 about lthe primary, the action of which effects rotation of the secondary without supplying an electrical current thereto as in the use of a commutator thereby reducing the weight. The weight has been further reduced by making the primary the inner or stationary part and the vsecondary the outer or rotatable part. By this arrangement the diameter of the air gap has been increased thus increasing the power of a small motor, a factor of the horsepower being the di.. 10o

Vthe belt 72 to run true on the pulleys.

ameter of the air squared times the length of the primary.

It has been found that a single pulley rotated in the manner develops sufiicient power to drive a polishing or sanding belt around an idler pulley which may be substituted for the one shown as a driving pulley. The pulleys are shown interchangeable, one rigidly supported on the housing l() and the other adjustably carried by the adjustable support 34. The portion 36 is provided with' apertures ill which receive a pin 7G. arm 78 is fitted over the portion 86 and is pivoted between a biurcated portion 8O o' the support 84. rlhe outer end of the arm 78 lis resiliently held as by a spring 8l against a screw threaded stop 82 carried by the support 34. By this arangement the pulley may be angnlarly positioned to caulse 'l` ie support Sil is longitudinally adjustable in the boss 32 to adjust the tension on the belt. It is resiliently held in one position by a spring 84: and positively held in the other direction by a threaded member 86 abuting against the boss 32. The support 34 has a projecting member 88 adapted to slide in an opening 90.A rl`he spring 84 is mounted on a cylindrical reduced portion 92 and is compressed between a shoulder 9f-l and the end Wall of the opening 90. The reduced portion extends thru the end wall and is provided with screw threads to receive the screw threaded member 86. By turning the member 86 in one direction the support and pulley is drawn inwardly against the spring resistance and by turning it in the opposite direction the spring 84 urges the support and pulley in the opposite direction.

Detachably secured to the boss 32 or hous ing 10 is a shoe member consisting of a plate 96 'to which is secured a felt pad 98. A- rubber pad 100 is held between the plate 96 and pad 98. The outer or lower surface of the felt pad 98 is coa-ted with graphite 99 t0 permit the belt 72 to easily slip thereon. The shoe is secured to the housing by screws 102 which may be removed to replace the shoe. The tool is supported on the shoe rather than the pulleys and the resilient belt backing permits the Working surface to conform to thesurface of the article being polished or sanded.

It will be understood that various changes may be made in the arrangement, combination and construction of the various parts of my invention without departing from the s irit thereof and it is not my intention to limit its scope other than by the terms of the appended claims.

What I claim is:

a device of the class described coinprising a housing adapted to be manually supported, a pair of pulleys rotatably supported by said housing, a belt having an maar?? abrasive surface around said pulleys, means tor rotating one ci? said pulleys, a resilient shoe carried by said housing lcoml'irising an outer yieldable felt pad and an inner resilient rubber pad, said shoe being adapted to urge said belt against relief irregularities on a piece of work with greater intensity than against surrounding regular surfaces.

2. In a device of the class described comprising a housing, a pair of pulleys rotatably supported by said housing, a. belt having an abrasive surface around said pulleys, means for rotating one of said pulleys, a resilient shoe carried by said housing having a felt pad backed by a rubber pad, and a graphite coating on the outer surface of said felt pad, said shoe adapted to urge a portion of said belt beyond its natural path of travel.

FREDERICK JOHNSON. 

